You just need to open a form "AR System user preference form" and create a entry for the user (if not already present) and specify the home page for that user.

Or else you can also set the global home page for all the users on from "Server information form- > configuration". If you set a form name here it would be applicable for all the users connected to current server.

Do you want to do a custom login page, authenticate and then redirect?

There are some informations in guide "BMC Remedy Action Request System 7.6.04 BMC Remedy Mid Tier Guide.pdf" that show you how to create a custom login pageor how to pass data / parameters using the url itself.